The Great Oxygenation Event Was a Time in the Middle

question 17

Multiple Choice

The Great Oxygenation Event was a time in the middle Proterozoic when

• A) organisms that produce oxygen first originated.
• B) oxygen began to accumulate as a gas in the atmosphere.
• C) the oxygen concentration in the atmosphere reached its present concentration of
• 21 percent.
• D) excessively high concentrations of oxygen in the atmosphere caused a mass extinction.

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Definitions:

Transition

The process or period of change from one state or condition to another.

Tabulations

The systematic arrangement of data in rows and columns, usually for the purposes of analysis or presentation.

Active Voice

A sentence construction in which the subject performs the action expressed by the verb, focusing attention on the doer of the action.

Enumerations

The act of counting or listing items sequentially.